In 3rd Generation Partnership Project (3GPP) Universal Mobile Telecommunication System (UMTS) R8 version, for a user equipment (UE) in idle mode or in the forward random access channel (CELL_FACH) state, in order to decrease an uplink transmission delay and improve an uplink transmission rate, an enhanced random access channel (RACH) is introduced, that is, an enhanced dedicated transport channel (E-DCH) substitutes for an RACH to implement uplink transmission.
A radio network controller (RNC) may configure an uplink transmission common enhanced dedicated transport channel (Common E-DCH) resource pool for a base station (NodeB). For example, the resource pool may have 32 sets of resources, where resource indexes (index) 1 to 32 are used to represent corresponding resources. The base station may allocate a common E-DCH resource to a user equipment according to the common E-DCH resource pool configured by the radio network controller.
The radio network controller configures two information elements (IE), Granted E-DCH Resources and Denied E-DCH Resources, on an Iub interface. The Granted E-DCH Resources are used to collect statistics on the number of E-DCH resources that are granted to a user equipment in a cell of the base station within a certain period. The Denied E-DCH Resources are used to collect statistics on the number of RACH preambles (preamble) that are detected at the base station but are denied to be allocated an E-DCH resource within a predefined period. The base station may report statistic values of the number of Granted E-DCH Resources and the number of Denied E-DCH Resources to the radio network controller in a mode set by the radio network controller, such as, periodic report, event triggered report, or on demand report. The radio network controller adjusts, according to the two statistic values, the number of common E-DCH resources configured for the cell.
The 3GPP UMTS R11 version introduces the feature that a 2 ms transmission time interval (TTI) and a 10 ms TTI coexist, that is, each cell is configured with two TTI lengths. In a same cell, a user equipment that supports an enhanced RACH, when performing uplink transmission, may dynamically select either of the two TTI lengths to perform uplink transmission. In this case, the user equipment may select a common E-DCH resource to which the 10 ms TTI corresponds or a common E-DCH resource to which the 2 ms TTI corresponds to perform uplink transmission. Because user equipments in a cell that select different TTI to perform uplink transmission change dynamically, how to dynamically adjust the range (or size) of a resource pool in the case that a plurality of TTI coexists is an urgent problem to be solved.